Transparent method
The formula
Worked example
Example inputs
How to interpret the result
The estimated glomerular filtration rate turns a blood creatinine level into a measure of how well the kidneys filter. The 2021 CKD-EPI equation, which no longer uses race, gives about 94.6 for a 45 year old man with a creatinine of 1.0, near the reference figure of 90. Creatinine depends on muscle mass, diet and hydration, so one reading can mislead. A value under 60 that persists for three months is one of the criteria clinicians use for chronic kidney disease.
Before you rely on it
What to check
Compare readings over time, taken under similar conditions, and give your clinician the lab's own eGFR. It may use a different equation for a specific case.
The common error
Where people go wrong with GFR calculator
Treating one result as a diagnosis. A single reading can shift with a hard workout, a dehydrated day or a meal of cooked meat.
Sensitivity evidence
How serum creatinine changes the estimated GFR (ml/min/1.73m²)
| Serum creatinine | Estimated GFR (mL/min/1.73m²) | Percent of normal (90 mL/min) function |
|---|---|---|
| 0.8 | 111.2 | 123.6% |
| 0.9 | 107.3 | 119.3% |
| 1worked example | 94.6 | 105.1% |
| 1.1 | 84.4 | 93.7% |
| 1.2 | 76 | 84.4% |
Every input, tested
Which input moves the estimated GFR (ml/min/1.73m²) most
| Input | Tested from | To | Estimated GFR (mL/min/1.73m²) at each end | Swing |
|---|---|---|---|---|
| Sex | Male | Female | 94.6 to 70.8 | 23.8 (25%) |
| Serum creatinine | 0.9 | 1.1 | 107.3 to 84.4 | 23 (24%) |
| Age | 34.0 years | 56.0 years | 101.3 to 88.3 | 13 (14%) |
Two variables at once
Estimated GFR (mL/min/1.73m²) by serum creatinine and age
| Serum creatinine \ Age | 23.0 years | 45.0 years | 67.0 years |
|---|---|---|---|
| 0.8 | 127.5 | 111.2 | 97 |
| 0.9 | 123.1 | 107.3 | 93.6 |
| 1 | 108.5 | 94.6 | 82.5 |
| 1.1 | 96.7 | 84.4 | 73.6 |
| 1.2 | 87.1 | 76 | 66.3 |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Sex | Male | The CKD-EPI equation uses different constants by sex. |
| Serum creatinine | 1 | From a recent blood test, in mg/dL. |
| Age | 45.0 years | Age in years. |
| Estimated GFR (mL/min/1.73m²) | 94.6 | |
| Percent of normal (90 mL/min) function | 105.1% | |
Inputs, definitions and assumptions
Sex
The CKD-EPI equation uses different constants by sex.
Serum creatinine
From a recent blood test, in mg/dL.
Age
Age in years.
Where the inputs come from
Enter your sex, age and serum creatinine from a blood test, in milligrams per deciliter. The 2021 CKD-EPI equation is the race-free version recommended in the United States for estimating glomerular filtration rate, the rate at which the kidneys clear blood. Use a recent, fasting-independent lab value and note that creatinine depends on muscle mass. The tool is for adults and is educational, not diagnostic.
Using the estimated GFR (ml/min/1.73m²) in a real decision
Discuss results and trends with a clinician.
When the result stops applying
Creatinine can be raised by a high-protein meal, dehydration, certain medications and high muscle mass, or be low in people with little muscle, which can mislead the estimate. Cystatin C can improve accuracy in such cases. The equation is not validated for children, pregnancy or acute kidney injury. Doctors also look at urine tests and imaging.
What to compare it with
See the Cockcroft-Gault creatinine clearance calculator, which is used for some drug dosing, and the blood pressure and cholesterol pages for related risk markers. The BMI and body surface area calculators give body size context. Talk with your doctor about any abnormal result.
People also ask
Frequently asked questions
What is a normal GFR?
Generally 90 or above, though it declines with age. Values under 60 for three months or more can indicate chronic kidney disease.
Why was the race adjustment removed from the equation?
Race is a social construct, and the 2021 equation was developed to estimate kidney function without it, which is now recommended by US kidney organizations.
Can one low eGFR result diagnose kidney disease?
No. Doctors confirm it with repeat tests over at least three months and other markers such as protein in the urine.